HIGH DENSITY FLOORING — FLOOR LOADS VS. DESIGN FLOOR LOADS

It’s About Uniform Building Codes

The subject of actual floor loading versus design floor loading is often misunderstood. Did you know that the Uniform Building Code requires, at a minimum, floors be designed to support the dead load of the floor and the required live load? For an office building, the live load is normally a uniform load of 50 pounds per square foot (psf) over the entire floor area for a framing member or a 2,000 pound load placed upon any 2 1/2 x 2 1/2 square foot space. The load producing the greatest stress in a framing member is the governing load for that member. The Load is an Average Value.

Here are 10 Things I Know About Floor Loading:

The requirement to design a floor for a uniform load of 50 PSF over the entire area for a particular member does not mean that this is the largest load that can be placed on the floor.

The load is an average value for a typical office space with desks, filing cabinets, aisles, etc. As can be seen by the concentrated load requirement, the 2,000 pounds in 6.25 square feet (2 ½ x 2 ½ ft) is a load of 320 PSF. This high loading assumes that the area around the concentrated load is unloaded. This would occur if the heavy object was surrounded by aisle space. Each loading condition must be reviewed individually.

The typical floor load for high density filing is 250 PSF. This is greater than the 50 PSF uniform design load. Since the design load is assumed over every square foot of floor area, including aisles, the floor is not overloaded if there is four square feet of aisle area for each square foot of file storage floor area. This statement is a simplification of the issue and cannot be used as a basis of approval for every high density storage application.

Each installation must be considered as a separate case. To avoid the danger of overloading the floor, the approximate weight of the system and the materials to be stored should be calculated and evaluated individually by a licensed architect or engineer.

As mobile storage increases the capacity in a given area, the weight of the system automatically increases. To verify whether a mobile storage system is within the approved floor loading weight as indicated by building specifications, the following calculations can be used. NOTE: It is extremely important to obtain the approved floor loading for each individual system and installation, prior to any calculations and final evaluations being made.

Determine the area the mobile system will utilize. Take the actual length and width and add 3’ to the width for the main walking aisle. In some cases, if the mobile system is the only equipment within a room, take the area of the entire room.

Calculate the weight of the system, including the mobile components, storage units and stored material. The mobile product and storage unit weights can be calculated from the estimate of what is to be included within the system. The weight of the stored material is calculated by multiplying the capacity (linear measurement) by the stored material weight (per linear measurement). NOTE: In many cases, a mobile system will never be loaded to more than 80% of its full capacity.

To obtain the total system loading weight, divide the total weight of the system by the system floor area.

Ensure the total system weight does not exceed the specified building floor loading.

10.Weight of Stored Material — Some commonly stored items and their approximate weights can help you to plan. For storage of other types of material – parts, industrial supplies, samples, dry goods, etc. – an estimate should be obtained.

Media

Lbs. /Inch

Lbs./Foot

Lbs. Per 36” Section

Letter size documents

2

24

70

Medical records

2

24

70

Legal size documents

2 ½

30

90

X-ray film w/jackets

8

96

280

Printouts (in binders)

3 ½

42

125

Books

1 ¼

15

45

You now have several methods for calculating and accommodating floor loads for high density shelving systems.

When working with an outside professional check their qualifications closely. Work with a structural engineer who has experience with the specific floor system involved. Equally important, you should work with a storage and filing system supplier who can give you the storage capacities and loads – both uniform and line loads. They should be knowledgeable in a wide variety of structural system design strategies. While floor loading issues are difficult and complex, structural engineers and firms like National Office Systems can help to guide you through the process without restriction to a single high density shelving manufacturer. Look for a company like National Office Systems in the Washington, DC and Mid-Atlantic Regions or Systematics in the Northeast who is open to creative solutions to achieve maximum space efficiency at a cost you can live with. For additional information not included in this post or for your specific interest, ask me your question here.

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